This invention relates to artificial resuscitation devices, and more particularly to equipment for controlling the frequency and volume of air, oxygen or oxygen enriched air to a patient.
Cardiopulmonary resuscitation (CPR) is a standard technique applied to victims of cardiopulmonary arrest in order to re-establish normal cardiac and respiratory function. The respiration component of CPR is typically provided with an apparatus including a self-filling rubber or silastic enclosure or bag which is elastically compressible by hand, a face fitting mask in fluid communication with an outlet passage of the bag, and a one-way valve between the mask and bag to permit fluid passage only from the bag to the mask. The bag also has an inlet passage, typically with one opening for air and another, usually smaller opening for receiving oxygen. By hand-squeezing the bag, a clinician delivers air or oxygen to the patient, then releases the bag to permit it to expand to full size and thereby draw air or oxygen through the inlet passage.
Depending upon such factors as body size, age and sex, adult victims of cardiopulmonary arrest may require tidal volumes ranging from eight hundred to two thousand cubic centimeters, supplied to the lungs at a frequency of about twelve cycles or strokes per minute for adequate respiration. A further variable factor is the amount or concentration of oxygen required by a particular patient. The oxygen concentration and pH of a patient's blood must be adjusted to and maintained at a desired level for optimum response to drugs or other treatment administered during or after CPR. Accordingly, it is highly desirable to determine the tidal volume, respiration frequency and oxygen concentration during CPR.
Presently available portable artificial respiration equipment is not suitable for the desired monitoring and control of tidal volumes delivered by the hand-squeezed resuscitation bag. Although self-filling resuscitation enclosures can be selected on the basis of known volumes, the volume actually delivered can vary substantially among several operators, dependent upon such factors as hand size, technique, enthusiasm and fatigue. For example, in one test of twenty individuals, actual delivered volume, measured as an average of ten strokes or squeezes using the same capacity resuscitation bag, ranged from just over 700 cc's to nearly 1150 cc's when one hand was used, and ranged from just over 850 cc's to nearly 1400 cc's when two hands were employed. The same individual delivers varying volumes as well, primarily due to fatigue over an extended administration of CPR. Of course, the problem in measuring total supply of air or oxygen is aggravated if the frequency of squeezing the resuscitation bag is uncertain.
Equipment for controlling the amount of air and/or oxygen supplied during artificial resuscitation is known. For example, in U.S. Pat. No. 1,197,232 (Pierpont), air or oxygen from a portable tank is supplied to a patient through hand-operable bellows. A wing nut is adjustable on a curved rod spanning the bellows to adjust the extent to which they can be opened. U.S. Pat. No. 2,902,992 (Renvall) discloses a bellows between horizontal fixed and movable end plates. Volume control is provided in the form of a stop mounted on one of the rods supporting the movable plate.
U.S. Pat. No. 3,890,967 (Elam) discloses a dual bellows between a patient and a hand-squeezed resuscitation bag. One of the bellows has a cross-sectional area considerably smaller than the other, so that the arrangement can act as an amplifier for the squeeze bag. A scale is provided to indicate the amount of air supplied.
Similar apparatus can be employed to supply anesthesia gas, as disclosed in U.S. Pat. No. 3,757,776 (Bauman) and U.S. Pat. No. 4,187,845 (Dror). Dror shows a flexible cable linkage between a bellows and a foot pedal, while the Bauman Patent shows a pair of opposed concave paddles for squeezing a flexible breathing bag. The paddles are electrically operated to control the frequency of their opening and closing cycle. A related manner for frequency control is disclosed in U.S. Pat. No. 4,297,999 (Kitrell), in which a portable resuscitation apparatus includes a battery operated rhythm unit to indicate a prescribed beat, either visually or aurally.
While adequate for certain uses, the above devices fall short of optimum suitability for emergency cardiopulmonary arrest situations.
Therefore, it is an object of the present invention to provide a means to adjustably control the maximum volume assumed by a conventional self-filling resuscitation enclosure.
Another object is to provide a means for adjusting the delivered fluid volume of a self-refilling resuscitation bag, and its cycle frequency, in accordance with the needs of a particular patient.
A further object is to provide a device for retrofitting standard artificial resuscitation self-filling bags and associated equipment to more precisely control the tidal volume and level of oxygen.
Another object of the invention is to provide a device that ensures that a variety of individual clinicians will expel substantially the same volume of fluid during each compression/re-inflation cycle.
Yet another object is to provide a retrofit device for a standard artificial resuscitation bag which affords a mechanical advantage to reduce user fatigue, yet provides the clinician with a tactile sense of patient lung compliance during artificial respiration.